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Your post is still not visible on the thread page, you should try to post everything as simple text
and not as an "overly-formatted" something ...
Anyway:
You are getting error because you SELECT a single row with an employee id ( 123 )
that DOES NOT exist in your table.
In such cases Oracle raises a NO_DATA_FOUND exception
and your code should handle this situation, depending on your application logic.
You can also let it propagated unhandled from the current procedure,
and handle it instead in a calling procedure or in your application that receives this exception.
I guess that this is just a sample procedure, because for the actions it performs
it is much easier and also much more recommended to use a SINGLE SQL UPDATE statement.
If your purpose is to learn PL/SQL then I can only suggest that you read the most basic
Oracle documentation which is the PL/SQL Language Reference. http://docs.oracle.com/cd/E11882_01/appdev.112/e25 519/toc.htm

It contains lots of examples and is "the must" first step for anybody who starts using
PL/SQL.
Best Regards,
Iudith